1. Field of the Invention
The present invention relates to devices and processes for determining the physical properties of Newtonian and non-Newtonian fluids, and, more particularly, to the testing of fluids by relatively movable mechanical elements in contact therewith.
2. The Prior Art
Various instruments have been proposed for testing viscoelastic properties of fluids, including surface tension, viscosity, shear stress, and yield point. Certain of such instruments involve relatively movable elements having bearing surfaces between which the fluid to be tested is placed. In each case, the force required to cause movement between the fluid-contacting elements is a function of the fluid's rheological properties. In such instruments, related difficulties are encountered in establishing reproducible test conditions and reproducibly maintaining the sample. Particularly in the case of non-Newtonian (i.e. non-ideal), multiphase polymeric fluids, such as milk, ketchup, mustard, blood, mucus, and saliva, the steps of pressing, shearing, separating, etc. cause homogenization, drying, etc.